Engine failure in the climb question
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Engine failure in the climb question
Ok all you bright sparks out there...my instinct may be wrong (and I hope it is) but I reckon you might well be on the way to meeting your maker if this should happen in an R22. Is there someone out there who can tell me how to work this out? I'm afraid my grasp of physics isn't quite up to the task...
60KIAS
500fpm ROC
Engine quits suddenly
1. How long will it take before you stop going up?
2. How long will it take before you establish a ROD airflow of sufficient magnitude to keep those low inertia blades spinning?
Low RRPM horn comes on at 97% and my guess is that most of us wouldn't have the collective on the floor until it got to this figure. That leaves 1.2 secs to establish an auto before RRPM becomes irrecoverable. Is it possible? If it is (at 500fpm ROC), at what ROC is it not? There has to be a ROC that shouldn't be exceeded. What is it?
Thanks for any answers.
60KIAS
500fpm ROC
Engine quits suddenly
1. How long will it take before you stop going up?
2. How long will it take before you establish a ROD airflow of sufficient magnitude to keep those low inertia blades spinning?
Low RRPM horn comes on at 97% and my guess is that most of us wouldn't have the collective on the floor until it got to this figure. That leaves 1.2 secs to establish an auto before RRPM becomes irrecoverable. Is it possible? If it is (at 500fpm ROC), at what ROC is it not? There has to be a ROC that shouldn't be exceeded. What is it?
Thanks for any answers.
Can't give you the specific answers, but can say it is possible to recover safely once above about 200 ft. Possible lower down too, but more tricky and you start to get into the grey area between failure in the low level cruise versus established climb, with the attendent differring entry techniques and time frames.
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The climb is an especially difficult case because the power input to the rotor is high, and the trimmed collective position is high, so the initial rotor decay is very fast. This makes the minimum rotor droop lower than in a level flight case, if everything else was equal. Combined is the fact that the climb inflow is farther away from autorotative flow means that there will be much more delay before the autorotative flow can drive the rotor.
Offsetting these negative effests is the fact that the tests performed for certification include auto entry in virtually all critical flight conditions, including climb. The FAA inserts a delay to simulate the reaction of an average pilot, and the climb is a maneuver state where the hand is actively trimming the power, so the delay in pilot reaction in a climb is very much less than a leisurely cruise. The FAA allows 1.3 seconds in cruise before down collective, but only .3 second for maneuver states such as the climb. This means that the auto entry is permitted to occur more quickly in tests (as it would be in reality). The net result is that auto entry from the climb should be not much worse than cruise.
Offsetting these negative effests is the fact that the tests performed for certification include auto entry in virtually all critical flight conditions, including climb. The FAA inserts a delay to simulate the reaction of an average pilot, and the climb is a maneuver state where the hand is actively trimming the power, so the delay in pilot reaction in a climb is very much less than a leisurely cruise. The FAA allows 1.3 seconds in cruise before down collective, but only .3 second for maneuver states such as the climb. This means that the auto entry is permitted to occur more quickly in tests (as it would be in reality). The net result is that auto entry from the climb should be not much worse than cruise.
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I was told that the 2000 ft/min climb restriction in the Bell 407 was due to the fact the if you were to lose an engine in fast climb it would take forever to start descending again and hence enter autorotation.
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So what's the preferred climb for R22 people bearing in mind the contrasting risks of being close to the ground and having high levels of blade pitch?
- minimum collective to achieve between 500 & 700fpm, or
- use all available power to get as high as possible as fast as possible
Obviously, take off location will have an impact, but assuming you have the freedom to decide.
BW
- minimum collective to achieve between 500 & 700fpm, or
- use all available power to get as high as possible as fast as possible
Obviously, take off location will have an impact, but assuming you have the freedom to decide.
BW
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The answers are common to all helos, not just the Robinson, frankly.
The climb limitation for most helos is generally due to the somewhat silly handling requirements of FAR, where the longitudinal stick stability is measured at max climb rate. Some helos have difficulties meeting it, so they impose a climb rate limit at the highest climb rate where the handling is still compliant.
We have Bell lurkers on pprune, wonder what they would tell us?
bladewashout asks a good question. Do we fly as if the engine will quit right now, and fly in every way to completely optimize the response to that failure? Best engine failure protection, for those who would completely slave their flight techniques to minimize the risk of engine failure: Stay Home.
It is a probabilities game we play when we fly, order a steak or pull down our pants. Because we train for engine failure, it becomes THE failure, and we focus on it as if it were the ONLY failure.
The climb limitation for most helos is generally due to the somewhat silly handling requirements of FAR, where the longitudinal stick stability is measured at max climb rate. Some helos have difficulties meeting it, so they impose a climb rate limit at the highest climb rate where the handling is still compliant.
We have Bell lurkers on pprune, wonder what they would tell us?
bladewashout asks a good question. Do we fly as if the engine will quit right now, and fly in every way to completely optimize the response to that failure? Best engine failure protection, for those who would completely slave their flight techniques to minimize the risk of engine failure: Stay Home.
It is a probabilities game we play when we fly, order a steak or pull down our pants. Because we train for engine failure, it becomes THE failure, and we focus on it as if it were the ONLY failure.
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Talking About Statistics and Probabilities.
Lets suppose we are well trained, Not flying robinsons, Flying Turbine (single), Not on water, Mostly corporate work, Flying Safe and with Caution, Doing a deep pre-flight before flight, stayed away from bozo mechanics, have a heli in well shape (maintainance wise and care wise), doing refreshers every year.
HERE ARE THE STATISTICS QUESTIONS:
1) Now supposing this, what are our odds as helicopter pilots who fly an average of 30 to 50 Hours a month, of making it alive until we can no longer fly because we did not passed our medical
?
2) What are our odds as helicopter pilots, who fly an average of 30 to 50 Hours a month, of having a flame out or a tail rotor failure, or a deep heavy emergency?
I allway's questions my self with this questions, not because i am scared, or because i want to see if i should continue flying or do the math or anything, but mainly for plain curiosity.
Any one has any kind of math?
SORRY about the not flying robinsons point (for those roby lovers), but the statistics for those helis wont help a lot improve the numbers here. I DO like robies, i trained my first time on those, and made my solo on those and i trully like them, but for the sake of this excersice, lets leave ALL pistons out.
THANKS!
HERE ARE THE STATISTICS QUESTIONS:
1) Now supposing this, what are our odds as helicopter pilots who fly an average of 30 to 50 Hours a month, of making it alive until we can no longer fly because we did not passed our medical
?2) What are our odds as helicopter pilots, who fly an average of 30 to 50 Hours a month, of having a flame out or a tail rotor failure, or a deep heavy emergency?
I allway's questions my self with this questions, not because i am scared, or because i want to see if i should continue flying or do the math or anything, but mainly for plain curiosity.
Any one has any kind of math?
SORRY about the not flying robinsons point (for those roby lovers), but the statistics for those helis wont help a lot improve the numbers here. I DO like robies, i trained my first time on those, and made my solo on those and i trully like them, but for the sake of this excersice, lets leave ALL pistons out.
THANKS!
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Fly the correct technique for the machine that you fly. Use minimum power for the climb and maintain highest recommended RRPM. Select the clearest departure into wind. Keep full concentration until after levelling to the cruise. What else can you do, you are all prepared so an EFATO should work out ok.
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Nick says:
" The climb limitation for most helos is generally due to the somewhat silly handling requirements of FAR, where the longitudinal stick stability is measured at max climb rate. Some helos have difficulties meeting it, so they impose a climb rate limit at the highest climb rate where the handling is still compliant "
yes, that is why the 407 is limited to 2000 fpm VSI, and you do have to watch it as you can easily hit the 2000 fpm in that rocket
" The climb limitation for most helos is generally due to the somewhat silly handling requirements of FAR, where the longitudinal stick stability is measured at max climb rate. Some helos have difficulties meeting it, so they impose a climb rate limit at the highest climb rate where the handling is still compliant "
yes, that is why the 407 is limited to 2000 fpm VSI, and you do have to watch it as you can easily hit the 2000 fpm in that rocket
The EFATO in the climb in the R22 used to be demonstrated to students at Bristow's Redhill FTS. From a standard climb at 60 KIAS and above 200 ft the engine failure was simulated with a throttle chop. (This was prior to the Robinson SN advising against throttle chops.) RRPM would fall to the flight minimum, or transiently slightly below, but recovered quickly as the lever was lowered and with a slight flare, that was generally progressed to form the 'flare' phase of the SEOL. Not fully established in auto, so high rate of descent; positive flare; generally no problems. The student 'repeat' of the FI demo was initiated by lowering the lever after the standard verbal warning of PEF...Go.
The exercise served to reinforce the importance of keeping one's hand on the lever when climbing...........the regulatory certification 'pilot intervention time' in this configuration would leave little margin. DON'T BE TEMPTED TO TRY THIS.
I think I am correct in saying that the only SEOL accidents the Bristow FTS had with the R22 were a high-speed low-level, gone wrong (in the bottom sector of the avoid curve) and a hover SEOL, where a cyclic input by the student left the aircraft temporarily balanced on one skid. It could have fallen either way, but unfortunately........
Anyway, in both cases everybody walked away.
At the risk of repeating myself (I've said similarly in the past about 'going to the edge' ) please leave we test pilots to do the 'exciting' stuff: note the advice on these pages but do fly your aircraft at all times within the flight manual limits and in accordance with the manufacturer's recommendations.
The exercise served to reinforce the importance of keeping one's hand on the lever when climbing...........the regulatory certification 'pilot intervention time' in this configuration would leave little margin. DON'T BE TEMPTED TO TRY THIS.
I think I am correct in saying that the only SEOL accidents the Bristow FTS had with the R22 were a high-speed low-level, gone wrong (in the bottom sector of the avoid curve) and a hover SEOL, where a cyclic input by the student left the aircraft temporarily balanced on one skid. It could have fallen either way, but unfortunately........
Anyway, in both cases everybody walked away.
At the risk of repeating myself (I've said similarly in the past about 'going to the edge' ) please leave we test pilots to do the 'exciting' stuff: note the advice on these pages but do fly your aircraft at all times within the flight manual limits and in accordance with the manufacturer's recommendations.
Last edited by idle stop; 13th Dec 2005 at 17:12.
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an engine faliure at 500 ft in the climb should not be too much trouble for the experienced pilot, remember a progressive flare will increase the time needed to lower the lever by several seconds. ok you got the lever down in time but then your faced with low RRPM but its a low inertia rotor so thats good because the RRPM will come back much quicker.
I would rather suffer a failure in a robbo at 500ft than say a much higher inertia machine like the bell 47, buts that just me
I would rather suffer a failure in a robbo at 500ft than say a much higher inertia machine like the bell 47, buts that just me
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To those who posted replies to my original question, thank you.
I would however ask if anyone can tell me if there is a formula for working out the time from failure to established auto, given any ROC, IAS and weight.
Nick, I agree with you with regard to the inflow angles and initial rotor decay being faster than it would be in the cruise. This is what initiated my original question. I have asked a few high-time instructors for their view and they have all said the same thing - work it out on paper, as having thought about it and discussed it for a while they have expressed concern. I've tried but can't get my head around the physics/math.
Idle stop said "please leave we test pilots to do the 'exciting' stuff". I agree - I'm not too keen on going out and finding the answer to my question by ending up in a smoking heap.
Cyclic flare said "an engine failure at 500 ft in the climb should not be too much trouble for the experienced pilot". In principle I agree, however what is your definition of an 'experienced' pilot? I suspect not all R22 pilots will fall into this category.
As I said in my original post, there must be a ROC which is too high to recover from should the engine quit suddenly. How does one work out what this is and how much influence does the forward speed factor have? What about your density altitude? The R22 POH doesn't state a maximum ROC. It just states under 'Airspeeds for safe operation' 60kts for takeoff & climbs and 53kts for max rate of climb.
I would hate to tell a student (I don't) that they can climb out at 1,000fpm all day if they like if the reality is that this is needlessly putting them in a potentially fatal position.
I know as helicopter pilots we fly around all day doing things which are potentially dangerous/fatal - that's the nature of our profession, however I would like to think that where possible we try to minimise the time spent in these flight envelopes. It's not that I want to dwell upon something which is unlikely (although it has happened) to occur but rather that I would just like a straightforward answer to what I think is a valid question.
Thanks again for any replies.
I would however ask if anyone can tell me if there is a formula for working out the time from failure to established auto, given any ROC, IAS and weight.
Nick, I agree with you with regard to the inflow angles and initial rotor decay being faster than it would be in the cruise. This is what initiated my original question. I have asked a few high-time instructors for their view and they have all said the same thing - work it out on paper, as having thought about it and discussed it for a while they have expressed concern. I've tried but can't get my head around the physics/math.
Idle stop said "please leave we test pilots to do the 'exciting' stuff". I agree - I'm not too keen on going out and finding the answer to my question by ending up in a smoking heap.
Cyclic flare said "an engine failure at 500 ft in the climb should not be too much trouble for the experienced pilot". In principle I agree, however what is your definition of an 'experienced' pilot? I suspect not all R22 pilots will fall into this category.
As I said in my original post, there must be a ROC which is too high to recover from should the engine quit suddenly. How does one work out what this is and how much influence does the forward speed factor have? What about your density altitude? The R22 POH doesn't state a maximum ROC. It just states under 'Airspeeds for safe operation' 60kts for takeoff & climbs and 53kts for max rate of climb.
I would hate to tell a student (I don't) that they can climb out at 1,000fpm all day if they like if the reality is that this is needlessly putting them in a potentially fatal position.
I know as helicopter pilots we fly around all day doing things which are potentially dangerous/fatal - that's the nature of our profession, however I would like to think that where possible we try to minimise the time spent in these flight envelopes. It's not that I want to dwell upon something which is unlikely (although it has happened) to occur but rather that I would just like a straightforward answer to what I think is a valid question.
Thanks again for any replies.
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When you stay out the grey area of the Height Velocity diagram you shouldn't have a problem.
That why there is one.
I don't know how the R-22's HV looks like but I'm pretty sure at 500 ft doing 60 you're (way) out.
For bringing your rotor rpm up I would suggest S-Turns, because you don't want to slow down below 60 kts. in a R-22/Schweizer
That why there is one.
I don't know how the R-22's HV looks like but I'm pretty sure at 500 ft doing 60 you're (way) out.
For bringing your rotor rpm up I would suggest S-Turns, because you don't want to slow down below 60 kts. in a R-22/Schweizer
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an engine failure at 500ft in the climb would most definately need a progressive flare to maintain rrpm. you would then be left with very little forward speed, then gentle forward stick to get the speed up for the flare.
wesp
you only need 60kt for the flare. The r22 can be flown a zero forward speed in the auto and also backwards flight is no problem in autorotation
wesp
you only need 60kt for the flare. The r22 can be flown a zero forward speed in the auto and also backwards flight is no problem in autorotation
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wesp:
Unless otherwise specified, the grey area in the HV diagram is for level flight. Don't assume an engine failure during a high powered at the edge of the 'safe' area will be easy to handle.
Wildwilly:
There is no formula for what you seek. The approximations that are typically made for helicopter performance will quickly fall apart as you transition from powered flight towards autorotation.
The answer for the required intervention time problem comes from flight test. If it's calculated for a climb, first a minimum Nr will be decided. Next, the time between an engine failure and pilot reaction will be increased until the extrapolation looks like a further increase in delay will reduce Nr below the minimum.
Nick mentioned an engine failure in a climb is demonstrated for certification. Check the applicable FARS/JARS/etc. to see what the requirement is if you need more details.
Matthew.
Unless otherwise specified, the grey area in the HV diagram is for level flight. Don't assume an engine failure during a high powered at the edge of the 'safe' area will be easy to handle.
Wildwilly:
There is no formula for what you seek. The approximations that are typically made for helicopter performance will quickly fall apart as you transition from powered flight towards autorotation.
The answer for the required intervention time problem comes from flight test. If it's calculated for a climb, first a minimum Nr will be decided. Next, the time between an engine failure and pilot reaction will be increased until the extrapolation looks like a further increase in delay will reduce Nr below the minimum.
Nick mentioned an engine failure in a climb is demonstrated for certification. Check the applicable FARS/JARS/etc. to see what the requirement is if you need more details.
Matthew.
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Letsby Avenue
U are probably right, i don't know if this worriness is common on low time pilots like myself (120 hrs), but i just can't be off the air... Its far riskier to stay on the ground for me, i can go crazy! VERY CRAZY if i stop flying.
It was more of a curiosity question.
It was more of a curiosity question.
Idlestop,
I think there was an accident prior to those you mention, when the a/c was first introduced. Didn't two instructors manage to get a skid caught under one of the white 'spots' on the grass, (actually a large metal disc) during the ground run after an EOL, and flip over? IIRC one of those involved used to have a sticker on his headset that said "no step" referring to the means by which his colleague exited the aircraft on its side!
BTW how's trix, will you be doing visiting this neck of the woods again?
I think there was an accident prior to those you mention, when the a/c was first introduced. Didn't two instructors manage to get a skid caught under one of the white 'spots' on the grass, (actually a large metal disc) during the ground run after an EOL, and flip over? IIRC one of those involved used to have a sticker on his headset that said "no step" referring to the means by which his colleague exited the aircraft on its side!
BTW how's trix, will you be doing visiting this neck of the woods again?
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We used to regularly practice simulated engine failures in the climb after t/o. However we avoided the "grey" area between initial transition and steady climb at 60 kt/max. con. power/200 ft for practice purposes. Rate of climb in the R22 is not the critical element. Having 60 kt on the clock is. From the steady climb, if you close the throttle quickly, you have just time to say "Oh ****" (or whatever you do say) before you slam the lever to the bottom as quickly as you can move your hand. The RRPM will get down to 97% if you do just this. Under these circumstances, ie at 2-500 ft, DO NOT FLARE. If you do, yes it will initially recover a bit of RRPM but subsequently, full auto will take longer to establish. Airflow through the disc is the good news in R22's. When you drop the lever, the nose will fall naturally - fine, it will help to maintain IAS. Remember, the attitude for 60 kt in the climb is more nose up than in the auto, so if you keep the attitude, the speed falls. This does not mean shove the stick forward, as this droops the RRPM and results in a high R of D which from 200 ft can cause problems judging the flare. In fact, from 200 ft, you actually don't completely establish normal auto and the flare, even from 60 kt does not give the normal response, and a run on landing is almost inevitable.
If the donkey goes quiet before you reach 60 kt, BE OUT OF THE AVOID AREA, the RRPM run down at lower speeds is dramatic. When I see Robinsons still with only 30 - 40 kt on at 100 - 200 ft, I think the pilots would benefit from a demo of the consequences of this, but at a much greater height (like 2000 ft).
If the donkey goes quiet before you reach 60 kt, BE OUT OF THE AVOID AREA, the RRPM run down at lower speeds is dramatic. When I see Robinsons still with only 30 - 40 kt on at 100 - 200 ft, I think the pilots would benefit from a demo of the consequences of this, but at a much greater height (like 2000 ft).
212man:
Thanks for putting me right on the earlier BHL EOL mishap.
Will call you at Anduki when I'm nearby in early to mid January and you can tell me all about the new toys (S-92 to Nick!) over a fruit juice or two: unless we can find something alcoholic!
Thanks for putting me right on the earlier BHL EOL mishap.
Will call you at Anduki when I'm nearby in early to mid January and you can tell me all about the new toys (S-92 to Nick!) over a fruit juice or two: unless we can find something alcoholic!